Electric discharge switch



1951 P. LEMAlGRE-VOREAUX 2,542,149

ELECTRIC DISCHARGE SWITCH Filed Jan. 22, 1947 3 E w k X J 1.. n f 049' CF 602% 0 inventor:

Fig.2 Pierre LEMAlGRE-VOREAUX,

iikforneys.

Patented Feb. 20, 195T ELECTRIC DISCHARGE SWITCH Pierre Lemaigre-Voreaux, Paris, France, assignor to Scciete Anonyme pour les Applications dc IElectricite et des Gaz-Rares-Etabiissements Claude-Paz et Silva, Paris, France Application January 22, 1947, Serial No. 723,551 In France August 27, 1945 Section 1, Public Law 690, August 8, 1946 Patent expires August 27, 1965 My invention relates to a gaseous electric discharge device and more particularly to what may be termed a no-power-loss relay for making and breaking an electric circuit.

It is known that some gaseous electric discharge apparatus, provided with bi-metallic members, may form switches possessing special characteristics that are suitable for different applications; for example, a glow discharge tube, one electrode of which is bi-metallic, may form a switch acting only above a predetermined voltage and be used, for example, to shunt an electrical apparatus when the voltage has risen to such a value thatit would damage that apparatus. On the other hand it is known to start a discharge lamp, provided with thermionic electrodes that are warmed by the discharge itself during working, by connecting one end of each of the electrodes to the source of current, inserting an impedance in series and connecting one to the other the opposed ends of each of the electrodes through two lei-metallic switches, each one of which is located near an electrode and is provided with a bi-metallic strip bearing a movable contact; these switches are closed when the bimetallic strips are cold, and make it possible for the electrodes, when voltage is applied, to warm up and so to emit electrons that ionise the gas; afterwards, the opening of the switches caused by the heat produced at the electrodes gives rise to the starting of the discharge in the lamp. This device has the drawback that, when it is desired to relight the lamp immediately after having switched it ofi, it cannot work at once, so that it cannot be used.

It is accordingly an object of the invention to provide a gaseous electric discharge relay tube which allows the pro-heating current to flow immediately when the device is connected to the source of current, even if the discharge lamp has just been switched off.

A further object of the invention is the provision of a gaseous electric discharge relay tube which consumes no energy when the lamp has been alight for some seconds.

Still further objects of the present invention will become obvious to those skilled in the art by reference to the accompanying drawing.

Referring to the drawing, given merely by way of example, Figure 1 represents a switch according to the invention and Figure 2 represents an application of such a switch.

Referring to Figure 1, the envelope is constituted by the glass tube I to which is Welded, the

2 Claims. (Cl. zoo-113.5)

stem 2; the latter is passed through by four conductors arranged as the vertices of a square. To the conductor 3 is fastened the electrode 1 constituted by a nickel rod, coated with graphite if desired. The conductors i and 5 bear the thermionic rod 8, which is a refractory metal wire helically wound and coated with electron emitting material. 011 the conductor 6 is placed the electrode 9, similar to the electrode 1, but comprising on its upper end the tungsten contact I0. One of the ends of the bi-metallic strip I2 is welded to the conductor 5 while the other bears a tungsten contact ll, similar to ID and coming into contact with the latter.

The exhausting of the apparatus by exhaust pumps is effected by the pipe Hi. This operation comprises, as is known for discharge apparatus, baking the apparatus and activating the filament 8 raised to a red heat in vacuum by impressing a suitable voltage between the conductors 4 and 5. When the vacuum in the switch is satisfactory, a gas or a gas mixture, the composition and the pressure of which depend upon the desired characteristics, is let into its envelope. One may also bring into the apparatus a small portion of a metal, the vapor of which modifies the switch atmosphere, for example the mercury drop M.

In Figure 2 is shown schematically the use of the above described switch for starting an electric discharge lamp. In that figure, l 5 represents a tubular lamp, the glass envelope of which is coated, on its inner face, with a layer of photoluminescent substances; l6 and it are tungsten electrodes covered with alkaline-earth oxides; they are constituted by helically wound filaments borne by the conductors l1 and I8 for one electrode and I1 and [8 for the other. The conductors I! and I1 are connected to the alternative current mains, for example a 220 volts network, one of them directly, the other through a reactance coil [9 and a switch 29. The conductor l 8 is connected to the terminal 3 of the switch, whereas conductor I8 is connected to the terminal 6. The switch is designed so that the starting voltage of an arc discharge between the electrodes I and 8 is smaller than the mains voltage but greater than the voltage existing between conductors l8 and !8' when the lamp is alight; that voltage is, for example, volts.

When one closes the main switch 20, the bi-metallic strip I2 is cold and contacts [0, H are contacting; a glow discharge, that is a discharge with strong cathodic voltage drop occurs between electrodes 1 and 8 and warms up the electrode 8; this results in the latter emitting electrons and in the above glow discharge being transformed into a rectified arc discharge (the oathode of which is the electrode 8), that is .a dis-- charge with'a 10W cathodic voltage drop. During the half-cycles when the discharge occurs,

the electric current flows through the electrodes l6 and I6 and warms them while the heat produced by the discharge causes the Warping of the bi-metallic strip, which results-in the opening of the contact I0, ll, hence the extinguishing of the arc discharge and the starting of the lamp, for the starting voltage of the lamp, the electrodes of which already emit electrons at"the moment of the above extingui hing, is below the starting voltage of a glow discharge between the non-thermionic electrode 1 and the rod' 9 and contact Ill. As soon as the lamp lights, the bimetallic strip begins to cool down and restoresthe contact 10, H,

It is thus apparent that according to the working -or not of the arc discharge in the switch, thebi-metallic strip breaks or restores the connection between the first and second electrodes.

This device brings about no power consump tion when the lamp is alight, for there flows then no current in the circuit connecting the ends I8 to l8 of the lamp electrodes Besides, the switch is ready to function even if the lamp is relighted immediately after having been switched off, for the current flows anew between- IIJ and II, as soon as the lamp is switched on. Moreover this device yields, with a suitable setting of the contact In, H" and aproper design of the bi-metallic strip during its manufacture, any desired warm-up-duration of the lamp electrodes beforethe starting, which is very advantageous for the lamp life. Finally, it is possible to give the switch a sufficiently small size to enable it to be placed in one of the lamp bearing sockets.

It thus becomes obvious to those skilledin the art that I have provided an improved gaseous electric discharge switch for use-in the placeof the ordinaryglow switch used to start discharge lamp. My switch provides a swift starting and I consumes no power durin the working of the lamp.

What I claim is:

lpAn electric switch provided with only two terminals, comprising, in an envelope containing an ionisable medium, a fixed contact connected to one of the terminals, a first electrode atleas't partlycoated with thermionic emissive material, a second electrode connected to the other terminal, a" controllable connection between the first electrode and the fixed contact, and a bimetallic member, controlling said connection and operable by the heat of discharges occurring between said electrodes.

2. An "electric switch provided with only two terminals, comprising in an envelope containingan-ionisable medium, a fixed contact connected to one of the terminals, a first and a second" electrode, said first electrode being at least partly coated with thermionic electron emissive"material-and comprising a bimetallic member operable by the heat of discharges occurring between said electrodes and 'cooperating with the fixed contact, said member-touching,- I

when co1d,'said contact and moving away Trom it when warmed up,-and the other terminal of the switch being connected with said second electrode. 1

PIERRE LEMAIGRE-VOREAUX.

REFERENCES 'CI'IED The followingreferences are of record in the file -of"this patent:

UNITED STATES PATENTS Number Name Date 1,951,112 W e1s= 1 Mar. 13, 1934 2,224,828 McCarthy 1 Dec. 10,1940 2,268,522 Abbott Dec. 30, 1941 2,274,399 Cook Feb. 24, 1942 2,284,103" Smitley' May 26, 1942- 2292376 Spencer"; Aug. 11, 1942- 2,296',062 Scott i -1 Sept. 15,1942 2,464,748 Hodgkins 1 Mar, 15, 1949' 

